Gymnema montanum improves endothelial function via inhibition of endoplasmic reticulum stress by activating Nrf2 signaling

Objective: To investigate the effects of Gymnema montanum leaf extract against endoplasmic reticulum (ER) stress-induced toxicity in endothelial cells.Methods: The immortalized endothelial hybrid cell, EA.hy926 was treated with different concentrations of Gymnema montanum leaf extract (0-100 μg/mL) and the ER stress inducer, tunicamycin. The cytotoxicity was assessed by MTT as well as lactate dehydrogenase and malondialdehyde levels were determined. The levels of ER stress markers, GRP78 and CHOP were analysed by Western blot assay. The Gymnema montanum leaf extract-mediated activation of nuclear factor erythroid 2-related factor 2 (Nrf2) was assessed by cell-based luciferase enzyme fragment complementation assay and antioxidant responsive element driven luciferase reporter assay. The levels of phosphoproteins of the MAPK pathway were analyzed using the Bioplex system. Results: A dose-dependent cytoprotective effect of Gymnema montanum leaf extract was observed in tunicamycin-induced toxicity. Gymnema montanum leaf extract significantly reduced lactate dehydrogenase activity and malondialdehyde levels in ER stress-induced endothelial cells. It also suppressed ER stress markers dose dependently and inhibited the phosphorylation of JNK, ERK, MEK and p38 MAPK in tunicamycin-induced endothelial cells. Moreover, Gymnema montanum leaf extract increased the expression of Nrf2 and its downstream targets in endothelial cells. Conclusions: Gymnema montanum leaf extract attenuates ER stress by increasing the expression of Nrf2 and its downstream genes.

Inhibitory activity of the peptides derived from buffalo prolactin on angiogenesis.

The peptide fragments obtained by cathepsin digestion of purified buffalo prolactin (buPRL) monomer have been characterized using SDS-PAGE and FPLC with regard to size and pI. Their antiangiogenic activity was tested in chick embryo chorioallantoic membrane (CAM) assay and the human endothelial cells wound healing assay. Antiangiogenic activity was observed in cathepsin-cleaved fragments from buPRL. Further, a peptide sequence 45A- 46Q-47G-48K-49G-50F-51I-52T-53M-54A-55L-56N-57S-58C, which matched with human somatostatin (hSST), a known antiangiogenic factor, was located in the second loop between the first and second α-helices in the threedimensional structure of buPRL, obtained by homology modelling. The synthetic peptide matching with SST sequence was found to exhibit antiangiogenic activity in both in vitro and ex vivo assays. It was also observed that all the peptides related to buPRL could antagonize the vascular endothelial growth factor (VEGF) and bradykinin (BK)- dependent production of endothelial nitric oxide (NO), which is a pre-requisite for endothelial tube formation. It is concluded therefore that an internal sequence in buPRL and peptide fragments derived from cathepsin-digested buPRL exhibit antiangiogenic activities.